Five basic categories of anatomical and electrophysiological experiments on the functional organization of the somatosensory system in primates and other mammals are proposed. 1) Microelectrode "mapping" methods will be used to define those regions of somatosensory cortex and thalamus that are characterized by systematic body representations. 2) The relationship of anatomical patterns of connections to body representations will be determined by studying connections and mapping representations in the same animals. 3) Immediate and progressive changes in cortical maps will be studied after peripheral nerve section and other manipulations. 4) Single unit recordings will be used to investigate the segregation of neuron types within representations and show how the modular or microorganization of cortex relates to the somatotopic representations. 5) Single unit recordings and measures of metabolic activity (2-Deoxyglucose autoradiography) under different stimulus conditions will be used to characterize overall differences in neuronal properties between representations.